Fix CI errors due to ubuntu 24.04 image rollout (#160)

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### Description

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CI [broke
recently](https://github.com/foxglove/schemas/actions/runs/12341162294/job/34439471378?pr=159)
because Python 3.7 is not supported for Ubuntu 24.04 x64. See
actions/setup-python#962. This fixes the
`python` job to use Ubuntu 22.04.

.github/workflows/ci.yml

@@ -64,7 +64,7 @@ jobs:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_PUBLISH_TOKEN }}
 
   python:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04 # Required for python 3.7
     defaults:
       run:
         working-directory: python